Apple MB417LL User Guide - Page 46

If you have two or more computers sharing an Internet connection, be sure that your network is set up properly. You need to know whether your ISP provides only one IP address or multiple IP addresses, one for each computer. If only one IP address is provided, then you must have a router capable of sharing the connection, also known as network address translation (NAT) or "IP masquerading." For setup information, check the documentation provided with your router or ask the person who set up your network. The AirPort Base Station can be used to share one IP address among multiple computers. For information about using an AirPort Base Station, check Mac Help or visit the AirPort Extreme website at www.apple.com/support/airport. If you can't resolve the issue using these steps, contact your ISP or network administrator. Problems with AirPort Extreme Wireless Communication If you have trouble using AirPort Extreme wireless communication  Make sure the computer or network you are trying to connect to is running and has a wireless access point.  Make sure you have properly configured the software according to the instructions that came with your base station or access point.  Make sure you are within antenna range of the other computer or the network's access point. Nearby electronic devices or metal structures can interfere with wireless communication and reduce this range. Repositioning or rotating the computer might improve reception. 46 Chapter 4 Problem, Meet Solution